I did that math on here a long time ago. As stated above though, barrel life is a very realtive and fluid term. Over 1/4" and it is garbage for a bench rest shooter. For a hunter that is crazy accurate and will remain plenty good for a long time. It is aso affected by how the barrel is treated, heated up a lot, and how it is cleaned. If you are casually shooting and hunting then it should be a while before you need to replace one, if ever. No one says you have to wait until your current barrel is toast to order a new one though.........